Variation in Preoperative Refraction Results Among Refractive Surgery Patients: A Comparison of Five Measurement Methods

Background: Accurate preoperative refraction is critical in refractive surgery planning. Manifest refraction (MR) remains the clinical gold standard but is time-consuming and operator-dependent. Alternative objective methods, including wavefront aberrometry and automated refraction, offer speed and objectivity, yet their agreement with MR varies, particularly regarding astigmatic components. Identifying which alternatives most closely approximate MR has direct clinical implications. Objective: To compare preoperative spherical equivalent (SE) refraction obtained by five measurement methods and identify which most closely agree with MR as potential clinical alternatives. Methods: Retrospective comparative study of 104 eyes (52 patients) at IIUM Eye Specialist Clinic (January-May 2021). Five methods were compared: MR, Wavefront Supported Custom Ablation (WASCA) aberrometer, Zeiss i.Profiler (ZIP), Righton Retinomax Handheld (RRH) autorefractor, and focimeter (FOCI). Pairwise comparisons used paired t-tests on SE values. Results: Significant pairwise differences were found between all five methods (P < 0.05), except ZIP vs. RRH (mean difference (MD) = 0.03 diopters (D); P = 0.753). The two methods with the smallest mean differences from MR were ZIP (MD = 0.20 D) and RRH (MD = 0.22 D), both below the 0.25 D clinical significance threshold. The largest discrepancy was between WASCA and FOCI (MD = 1.44 D). Conclusion: Both the ZIP and RRH autorefractors produced SE values in close agreement with MR. ZIP is preferred due to superior positional control, yielding more reproducible astigmatic readings. Routine autorefraction with ZIP may supplement MR in preoperative refractive surgery assessment.